Mesenteric cyclooxygenase products after combined antihypertensive treatment in uninephrectomized SHRs

Unilateral nephrectomy in the spontaneously hypertensive rat (SHR) does not produce any change in blood pressure but does induce humoral alterations t hat might influence the antihypertensive action of some drugs. In this stud y, the antihypertensive effect of treatment (5 weeks) with placebo (control ), verapamil, trandolapril, or their combination (verapamil plus trandolapr il) was investigated in SHRs with half renal mass ablation, regarding the s tructure and function of small mesenteric arteries. Arterial pressure was f ollowed during the period of treatment. Trandolapril and veratran returned pressure to normal, while verapamil was ineffective. Statistically signific ant differences in the parameters of vessel structure were not observed amo ng groups; thus, the alterations in functionality cannot be attributed to m orphologic changes. The noradrenaline-induced contraction was reduced simil arly by the three treatments as compared to controls. This difference invol ved a higher participation of nitric oxide in the trandolapril group, while in the verapamil group the origin of the difference might be due to the ab olishment of a cyclooxygenase product. Veratran retained both effects. Acet ylcholine-evoked relaxation of vessels precontracted with noradrenaline was improved with treatments versus controls. The abolishment of a contracting prostanoid or an NO scavenger from the cyclooxygenase pathway, due to the treatments implemented, is probably the cause of this.